1. Field of the Invention
The present invention relates to a claw unit with paired separably connected claw elements, which is used for NC lathe or the like and, more particularly, to a claw unit with such paired claw elements, master jaw and top jaw, which permits the top jaw to be mounted on the master jaw, or separated therefrom for replacement in a simple manner.
2. Description of the Prior Art
Japanese Patent Unexamined Publication Nos. 60-201806 and 61-279403 disclose a claw unit with a pair of separably connected claw elements, master jaw and top jaw, which permits the top jaw to be mounted or demounted for replacement by way of a one-touch operation. In this claw unit, the master jaw is mounted, as disclosed in said literatures, with a clamp pin device which is equipped interiorly with a positioning pin so that the latter may protrude from, or retreat into, the clamp pin device. On the other hand, the top jaw is formed therein with an eccentric hole into which the clamp pin device is to be inserted, the eccentric hole being formed at a portion thereof with a groove. Whereby, a chuck involved is moved after insertion of the clamp pin device into the eccentric hole of the top jaw, to cause a flange portion of the clamp pin device to be fitted into the groove of the eccentric hole, thereby locking the top jaw to the master jaw.
According to the above-described conventional claw unit, however, it is not easy to effect aligning of the protruded portion of the master jaw with respect to the eccentric hole of the top jaw. This requires the machining of each element with high accuracy. According to the extent of accuracy to which each element is machined, it is impossible to effect a reliable aligning between the master jaw and the top jaw. This often results in locking and supporting of the top jaw by the clamp pin device only. This makes unstable the state wherein the top jaw is locked and supported. Further, when the top jaw is misaligned, or according to the manner in which some unbalanced forces are applied, it is possible that the top jaw is locked at some other position than its proper position, and thus becomes inseparable.